When he arrived at Ma Tso Lung in Sheung Shui an hour later, he used his Samsung Galaxy S7 mobile phone to check on Facebook and sent some pictures to friends through WhatsApp.

Shortly after he received several short messages from operator 3 Hong Kong stating that he had used 67.8MB of data roaming – at a cost of HK$10,425.

However, his wife, who uses the same operator, did not receive any short messages for any data roaming she used.

Pang was very shocked to receive such a big bill within Hong Kong territory, and suspected that his phone might have turned on data roaming services after updating automatically two days earlier.

He filed a complaint to the Communications Authority against the mobile operator, HK01.com reported. The authority advised that roaming data services should be turned on only when needed.

Pang said he was later told by operator 3 Hong Kong that he only has to pay a daily data plan of HK$138 – and it will spend two weeks to check whether he used data roaming services within Hong Kong or in the mainland, Headline Daily reported.

If the services were used in Hong Kong, Pang would get a refund for the HK$138.

3 Hong Kong said mobile phones in rural areas may sometimes connect with Chinese mobile operators’ networks, and that would result in a higher roaming data fee.